黄土路堑边坡变形破坏机理的三轴试验研究
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摘要
通过原状黄土的减压三轴压缩试验,研究了黄土边坡不同深度不同含水量土体的应力-应变关系,并与原状黄土的常规三轴试验结果进行了比较,发现减压三轴试验能合理地模拟和解释开挖卸荷作用下黄土边坡土体的变形与破坏过程。试验结果表明:坡脚开挖卸荷时,黄土边坡中浅层非饱和黄土易出现应变软化或塑性流动,强度较低,易产生较大变形,而深层饱和黄土仅在高围压下发生应变硬化,强度增加,在中低围压时均发生应变软化现象。分析认为黄土边坡特殊的工程地质条件,使得黄土边坡的特定部位在开挖卸荷作用下常形成了不利于土体稳定的含水量和围压组合,导致坡体特定部位的土体变形破坏,进而诱发边坡的变形破坏;开挖卸荷作用下黄土边坡变形破坏的力学机制应为蠕滑-压致拉裂或"牵引式滑坡"。
The stress-strain relationship of loess with different depth and water content of loess slope is studied with the reduced triaxial compress test of undisturbed loess and compared with the results of conventional triaxial compress test of undisturbed loess. It is pointed that the deformation and failure process of loess slope under excavation and unloading can be reasonably explained by the reduced triaxial compress test. The test results show that the surface unsaturated loess of loess slope with toe excavation is easy to appear strain softening or plastic flow, and strength reduction, the deep layer saturated loess appears strain softening under the condition of mid-lower confining pressure and strain hardening and strength increase under high confining pressure. Then, based on the results of reduced triaxial compress test, deformation mechanism analysis of loess cut slope is made. It is considered that the particular engineering geological conditions of loess slope leads to a disadvantageous combination of water content and confining pressure to the strength of soil. Then the disadvantageous combination causes deformation and failure of soil mass and slope. The deformation and failure mechanism of loess slope under excavation belongs to creeping slide and crack arising from pressing or retrogressive slide.
The stress-strain relationship of loess with different depth and water content of loess slope is studied with the reduced triaxial compress test of undisturbed loess and compared with the results of conventional triaxial compress test of undisturbed loess. It is pointed that the deformation and failure process of loess slope under excavation and unloading can be reasonably explained by the reduced triaxial compress test. The test results show that the surface unsaturated loess of loess slope with toe excavation is easy to appear strain softening or plastic flow, and strength reduction, the deep layer saturated loess appears strain softening under the condition of mid-lower confining pressure and strain hardening and strength increase under high confining pressure. Then, based on the results of reduced triaxial compress test, deformation mechanism analysis of loess cut slope is made. It is considered that the particular engineering geological conditions of loess slope leads to a disadvantageous combination of water content and confining pressure to the strength of soil. Then the disadvantageous combination causes deformation and failure of soil mass and slope. The deformation and failure mechanism of loess slope under excavation belongs to creeping slide and crack arising from pressing or retrogressive slide.
引文
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[2]王恭先.滑坡防治方案的选择与优化[J].岩石力学与工程学报,2006,25(Supp.2):3867~3873.Wang Gongxian.Choice and optimization of landslide control plan.Chinese Journal of Rock Mechanics and Engineering,2006,25(supp.2):3867-3873.
[3]王传仁.公路工程与滑坡灾害[A].滑坡文集(第十四集)[C].北京:中国铁道出版社,2000.Wang Chuanren.Highway engineering and landslide hazards.Landslide Symposium(Vol.14).Beijing:China Railway Publish-ing House,2000.
[4]Derbyshire Ed.Geological hazards in loess terrain,with particularreference to the loess regions of China[J].Earth-Science Re-views,2001,54(1~3):231~260.
[5]Dijkstra TA.Geotechnical thresholds in the Lanzhou loess of Chi-na[C].Quaternary International,2001,76~77,21~28.
[6]Sassa Kyoji.Undrained dynamic-loading ring-shear apparatus and its application to landslide dynamics[J].Landslides,2004,1,7~19.
[7]Baumler Rupter.Pedogenic studies in Aeolian deposit in the high mountain area of eastern Nepal[J].Quaternary International,2001,93~102.
[8]王家鼎,肖树芳,张倬元.灌溉诱发高速黄土滑坡的运动机理[J].工程地质学报,2001,9(3):241~246.Wang Jiading,Xiao Shufang,Zhang Xhuoyuan.The mechanism for movement of irrigation-induced high-speed loess landslides.Journal of Engineering Geology,2001,9(3):241~246.
[9]王家鼎,张倬元.地震诱发高速黄土滑坡的机理研究[J].岩土工程学报,1999,21(6):670~674.Wang Jiading,Zhang Zhuoyuan.A study on the mechanism of high-speed loess landslides induced by earthquake.Chinese Journal of Geotechnical Engineering,1999,21(6):670~674.
[10]吴玮江,王念秦.黄土滑坡的基本类型与活动特征[J].中国地质灾害与防治学报,2002,13(2):36~40.Wu Weijiang,Wang Nianqin.Basic types and active features loess landslides.Chinese Journal of Geological Hazard and Control,2002,13(2):36~40.
[11]程谦恭,张倬元,崔鹏.平卧“支撑拱”锁固滑坡动力学机理与稳定性判据[J].岩石力学与工程学报,2004,23(17):2855~2864.Cheng Qiangong,Zhang Zhuoyuan.Cui Peng.Dynamical mecha-nism and stability criterion of landslide under lockup of soil arc-hing.Chinese Journal of Rock Mechanics and Engineering,2004,23(17):2855~2864.
[12]党进谦,李靖.非饱和黄土的结构强度与抗剪强度[J].水利学报,2001,32(7):79~83.Dang Jinqian,Li Jing.The structural strength and shear strength of unsaturated loess.Journal of Hydraulic Engineering2001,32(7):79~83.
[13]邵江,李仁成,周德培,谢红强.近水平红层路堑边坡滑动机理和防治对策[J].工程地质学报,2005,13(2):174~178.Shao Jiang,et al..Preliminary study of the slip mechanism and the stoping method on the landslide of the approximately horizon-tal excavated slope in red beds.Journal of Engineering Geology,2005,13(2):174~178.
[14]赵建军,黄润秋,巨能攀,涂国祥,肖华波.下伏软弱层黄土边坡变形机制分析及治理对策研究[J].工程地质学报,2006,14(6):743~748.Zhao Jianjun,et al..Deformation mechanism of loess slope with weak interlayer and its stabilization measures.Journal of Engi-neering Geology,2006,14(6):743~748.
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